The now-defunct U.S. Government Agency "Office of the Coordinator of Inter-American Affairs" hired Walt Disney Studios to create a series of films for developing countries, "Health For The Americas."
"The Unseen Enemy" explains that disease is caused by tiny little creatures, which can be seen in a microscope.
As always, any error or typo is mine and if you enjoy my uploads or if you intend to make $ or otherwise profit from these files, please consider making a donation to a veteran's charity of your choice and/or Archive.org itself. Thanks. :)